Strongyloidiasis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Strongyloidiasis is a human parasitic disease caused by the nematode (roundworm) Strongyloides stercoralis, or sometimes S. fülleborni. It can cause a number of symptoms in people, principally skin symptoms, abdominal pain, diarrhea and weight loss. In some people, particularly those who require corticosteroids or other immunosuppressive medication, Strongyloides can cause a hyperinfection syndrome that can lead to death if untreated. The diagnosis is made by blood and stool tests. The drug ivermectin is widely used in the treatment of strongyloidiasis.
Historical Perspective
Strongyloidiasis was first described in France in 1876.
Pathophysiology
Strongyloides is classified as a soil-transmitted helminth. The primary mode of infection is through contact with soil that is contaminated with free-living larvae. When the larvae come in contact with skin, they are able to penetrate it and migrate through the body, eventually finding their way to the small intestine where they burrow and lay their eggs. Unlike other soil-transmitted helminths such as hookworm and whipworm whose eggs do not hatch until they are in the environment, the eggs of Strongyloides hatch into larvae in the intestine. Most of these larvae will be excreted in the stool, but some of the larvae may molt and immediately re-infect the host either by burrowing into the intestinal wall, or by penetrating the perianal skin. This characteristic of Strongyloides is termed auto-infection. The significance of auto-infection is that unless treated for Strongyloides, persons may remain infected throughout their lifetime.
Epidemiology and Demographics
It is thought to affect 30–100 million people worldwide, mainly in tropical and subtropical countries. Worldwide efforts are aimed at eradicating the infection in high-risk groups.
Diagnosis
History and symptoms
Strongyloides infection occurs in five forms. On acquiring the infection, there may be respiratory symptoms (Löffler's syndrome). The infection may then become chronic with mainly digestive symptoms. On reinfection (when larvae migrate through the body), there may be respiratory, skin and digestive symptoms. Finally, the hyperinfection syndrome causes symptoms in many organ systems, including the central nervous system.[1][2]
Physical examination
The physical examination findings in strongyloidiasis vary and it is usually dependent on the worm burden and the involved organ.
Laboratory findings
The gold standard for the diagnosis of strongyloides is serial stool examination. Duodenal aspirate is more sensitive than stool examination, and duodenal biopsy may reveal parasites in the gastric crypts, in the duodenal glands, or eosinophilic infiltration in the lamina propria. In disseminated cases of strongyloidiasis, larvae can be detected in sputum by simple wet-mount in fluid from a bronchoalveolar lavage (BAL). Immunodiagnostic tests for strongyloidiasis are indicated when the infection is suspected and the organism cannot be demonstrated by duodenal aspiration, string tests, or by repeated examinations of stool. Enzyme immunoassay (EIA) is currently recommended because of its greater sensitivity (90%). Cross-reactions in patients with filariasis and some other nematode infections can occur. Antibody test results cannot be used to differentiate between the past and current infection.
Chest and Abdominal Xrays
Radiographs can be useful investigations in the diagnosis of ascariasis. A chest x-ray can reveal varying sizes of oval or round infiltrates (löffler's syndrome). Plain abdominal radiographs and contrast studies can reveal worm masses in bowel loops.
CT
There are no specific CT findings associated with strongyloidiasis.
Ultrasound
There are no specific ultrasound findings associated with strongyloidiasis.
Treatment
Medical Therapy
The drug of choice for the treatment of uncomplicated strongyloidiasis is ivermectin with albendazole as the alternative. All patients who are at risk of disseminated strongyloidiasis should be treated. (Albendazole is approved by the FDA, but considered investigational for this purpose).[3]
Surgery
Strongyloidiasis is usually managed conservatively with medical therapy but surgery may be indicated when medical management fails or complications arise.
Prevention
The prevention of strongyloidiasis is best achieved through improvements in personal hygiene and environmental sanitation.
References
- ↑ Montes M, Sawhney C, Barros N (2010). "Strongyloides stercoralis: there but not seen". Curr Opin Infect Dis. 23 (5): 500–4. doi:10.1097/QCO.0b013e32833df718. PMC 2948977. PMID 20733481. Unknown parameter
|month=ignored (help) - ↑ Marcos LA, Terashima A, Dupont HL, Gotuzzo E (2008). "Strongyloides hyperinfection syndrome: an emerging global infectious disease". Trans R Soc Trop Med Hyg. 102 (4): 314–8. doi:10.1016/j.trstmh.2008.01.020. PMID 18321548. Unknown parameter
|month=ignored (help) - ↑ http://www.dpd.cdc.gov/dpdx/HTML/Strongyloidiasis.htm